U.S. patent number 8,080,281 [Application Number 12/412,984] was granted by the patent office on 2011-12-20 for growth and applications of ultralong carbon nanotubes.
This patent grant is currently assigned to Pohang University of Science and Technology, The Trustees of Columbia University in the City of New York. Invention is credited to Byung Hee Hong, Kwang S. Kim, Philip Kim, Ju Young Lee.
United States Patent |
8,080,281 |
Kim , et al. |
December 20, 2011 |
**Please see images for:
( Certificate of Correction ) ** |
Growth and applications of ultralong carbon nanotubes
Abstract
Ultralong carbon nanotubes can be formed by placing a secondary
chamber within a reactor chamber to restrict a flow to provide a
laminar flow. Inner shells can be successively extracted from
multi-walled carbon nanotubes (MWNTs) such as by applying a lateral
force to an elongated tubular sidewall at a location between its
two ends. The extracted shells can have varying electrical and
mechanical properties that can be used to create useful materials,
electrical devices, and mechanical devices.
Inventors: |
Kim; Philip (New York, NY),
Hong; Byung Hee (Seoul, KR), Lee; Ju Young
(Daegu, KR), Kim; Kwang S. (Pohang, KR) |
Assignee: |
The Trustees of Columbia University
in the City of New York (New York, NY)
Pohang University of Science and Technology (Pohang
Gyungbuk, KR)
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Family
ID: |
39230816 |
Appl.
No.: |
12/412,984 |
Filed: |
March 27, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090297847 A1 |
Dec 3, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/US2007/020778 |
Sep 26, 2007 |
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60848023 |
Sep 27, 2006 |
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60848024 |
Sep 27, 2006 |
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60848026 |
Sep 27, 2006 |
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Current U.S.
Class: |
427/249.1;
977/752; 977/742 |
Current CPC
Class: |
B01J
21/185 (20130101); C01B 32/162 (20170801); C01B
32/168 (20170801); B01J 23/745 (20130101); B82Y
30/00 (20130101); B82Y 40/00 (20130101); D01F
9/127 (20130101); Y10S 977/742 (20130101); Y10T
428/2918 (20150115); C01B 2202/06 (20130101); C01B
2202/34 (20130101); Y10S 977/752 (20130101) |
Current International
Class: |
C23C
16/00 (20060101); B32B 1/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO-2008/039496 |
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Apr 2008 |
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WO |
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WO-2008039496 |
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Apr 2008 |
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WO |
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WO-2008039496 |
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Apr 2008 |
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WO |
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Other References
"International Application Serial No. PCT/US2007/020778
International Search Report mailed May 29, 2008", 7 Pgs. cited by
other .
Collins, P, G., et al., "Engineering carbon nanotubes and nanotube
circuits using electrical breakdown", Science, 292(5517), (Apr. 27,
2001), 706-9. cited by other .
Cumings, J., et al., "Low-friction nanoscale linear bearing
realized from multiwall carbon nanotubes", Science, 289(5479),
(Jul. 28, 2000), 602-4. cited by other .
Cumings, J., et al., "Peeling and sharpening multiwall nanotubes",
Nature, 406(6796), (Aug. 10, 2000), 586. cited by other .
Hong, B. H, et al., "Extracting subnanometer single shells from
ultralong multiwalled carbon nanotubes", Proceedings of the
National Academy of Science.vol. 102(4), (2005), 14155-14156. cited
by other .
Kim, K. S., et al., "Molecular Clusters of pi-Systems: Theoretical
Studies of Structures, Spectra, and Origin of Interaction
Energies", Chem Rev., 100(11), (Nov. 8, 2000), 4145-86. cited by
other .
Kolmogorov, A. N., et al., "Smoothest bearings: interlayer sliding
in multiwalled carbon nanotubes", Phys Rev Lett., 85(22), (Nov. 27,
2000), 4727-30. cited by other .
"International Application Serial No. PCT/US07/20778, International
Search Report mailed May 29, 2008", 3 pgs. cited by other .
"International Application Serial No. PCT/US07/20778, Written
Opinion mailed May 29, 2008", 7 pgs. cited by other .
Hong, B. H., et al., "Quasi-Continuous Growth of Ultralong Carbon
Nanotube Arrays", Journal of American Chemical Society, 127,
(2005), 15336-15337. cited by other .
Kim, K. S., et al., "Molecular Clusters of .pi.-Systems:
Theoretical Studies of Structures, Spectra, and Origin of
Interaction Energies", Chem Rev., 100(11), (Nov. 8, 2000),
4145-4185. cited by other.
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Primary Examiner: Turocy; David
Assistant Examiner: Miller, Jr.; Joseph
Attorney, Agent or Firm: Schwegman, Lundberg & Woessner,
P.A.
Parent Case Text
CLAIM OF PRIORITY
This patent application is a continuation under 35 U.S.C. 111(a) of
International Application No. PCT/US2007/020778, filed Sep. 26,
2007 and published as WO 2008/039496 on Apr. 3, 2008, which claimed
priority under 35 U.S.C. 119(e) to U.S. Provisional Ser. No.
60/848,023, entitled GROWTH AND APPLICATIONS OF ULTRALONG CARBON
NANOTUBE ARRAYS, filed on Sep. 27, 2006; U.S. Provisional Patent
Application Ser. No. 60/848,024, entitled QUASI-CONTINUOUS GROWTH
OF ULTRALONG CARBON NANOTUBE ARRAYS, filed on Sep. 27, 2006; and
U.S. Provisional Patent Application Ser. No. 60/848,026, entitled
EXTRACTING SUBNANOMETER SINGLE SHELLS FROM ULTRALONG MULTIWALLED
CARBON NANOTUBES, filed on Sep. 27, 2006; which applications and
publication are incorporated herein by reference and made a part
hereof.
This patent application claims priority under 35 U.S.C. 119(e) to:
(1) U.S. Provisional Patent Application Ser. No. 60/848,024,
entitled QUASI-CONTINUOUS GROWTH OF ULTRALONG CARBON NANOTUBE
ARRAYS, filed on Sep. 27, 2006, which is incorporated herein by
reference; and (2) U.S. Provisional Patent Application Ser. No.
60/848,026, entitled EXTRACTING SUBNANOMETER SINGLE SHELLS FROM
ULTRALONG MULTIWALLED CARBON NANOTUBES, filed on Sep. 27, 2006,
which is incorporated herein by reference.
Claims
What is claimed is:
1. A method, comprising: providing a first gaseous flow in a first
chamber region; and dividing the first gaseous flow to provide, in
a second chamber region located within the first chamber region, a
second gaseous flow that is less turbulent than the first gaseous
flow; housing a substrate for forming a multi-walled carbon
nanotube within the second chamber region; and forming the
multi-walled carbon nanotube, using the substrate, in a direction
that is substantially parallel to a direction of the second gaseous
flow.
2. The method of claim 1, wherein forming the multi-walled carbon
nanotube comprises forming a multi-walled carbon nanotube of length
exceeding 10 centimeters.
3. The method of claim 1, wherein the multi-walled carbon nanotube
comprises first and second ends and an elongated side extending
between the first and second ends, the multi-walled carbon nanotube
including at a least lower order carbon nanotube, wherein the lower
order carbon nanotube comprises a carbon nanotube that is formed
within another carbon nanotube, the method further comprising:
extracting at least one lower order carbon nanotube from within the
multi-walled carbon nanotube via the elongated side of the
multi-walled nanotube.
4. The method of claim 3, wherein extracting includes successively
extracting lower order nanotubes.
5. The method of claim 3, wherein extracting includes extracting a
double-walled nanotube.
6. The method of claim 3, wherein extracting includes extracting a
lower order nanotube with a different conductivity property than
the multi-walled carbon nanotube.
7. The method of claim 3, comprising supporting the at least one
extracted lower order nanotube by a substrate.
8. The method of claim 3, comprising applying pressure to the
elongated side of the multi-walled carbon nanotube to rupture the
side of the multi-walled nanotube before performing the
extracting.
9. The method of claim 8, further comprising: coupling a probe to
the elongated side of the multi-walled carbon nanotube; using the
probe, moving the multi-walled carbon nanotube in a direction
perpendicular to a longitudinal direction of the multi-walled
carbon nanotube; breaking an outer portion of the multi-walled
carbon nanotube, using the probe, thereby exposing at least one
lower order carbon nanotube; and extracting at least one lower
order carbon nanotube through a first break in the outer portion of
the multi-walled carbon nanotube.
10. The method of claim 9, further comprising breaking an outer
portion of at least one lower order carbon nanotube, thereby
exposing at least one further lower order carbon nanotube.
11. The method of claim 1, wherein forming the multi-walled carbon
nanotube includes forming the multi-walled nanotube with a length
limited by at least one of: a dimension of a surface, a dimension
of a substrate, a dimension of a heated zone, or a flow
characteristic.
12. The method of claim 1, further comprising selecting a size of
the first chamber region and the second chamber region and
positioning the second chamber region in the first chamber region
so that the second gaseous flow is less turbulent than the first
gaseous flow.
13. The method of claim 1, comprises further comprising at least
one of adjusting a pressure within the first chamber region or
adjusting a pressure within the second chamber region.
Description
TECHNICAL FIELD
This document relates generally to nanotechnology, and more
particularly, but not by way of limitation to growth and
applications of ultralong carbon nanotubes.
BACKGROUND
Carbon nanotubes include generally tubular structures having a
diameter on the order of a nanometer. Carbon nanotubes can provide
unique electrical, mechanical, electro-optical, or
electromechanical properties. Therefore, they may be useful as
building blocks, such as for nanoscale electronic devices,
molecular sensors, or the like.
OVERVIEW
Ultralong carbon nanotubes can be formed by placing a secondary
chamber within a reactor chamber to restrict a flow to provide a
laminar flow. Inner shells can be successively extracted from
multi-walled carbon nanotubes (MWNTs) such as by applying a lateral
force to an elongated tubular sidewall at a location between its
two ends. The extracted shells can have varying electrical and
mechanical properties that can be used to create useful materials,
electrical devices, and mechanical devices. This document provides
numerous examples in the detailed description, an overview of which
is included below.
Example 1 describes a method. In this example, the method comprises
providing a multi-walled carbon nanotube. The multi-walled carbon
nanotube comprise first and second ends and an elongated side
extending between the first and second ends. The multi-walled
carbon nanotube includes at least lower order carbon nanotube. The
lower order carbon nanotube comprises a carbon nanotube that is
formed within another carbon nanotube. In this example, the method
also comprises extracting at least one lower order carbon nanotube
from within the multi-walled carbon nanotube via the elongated side
of the multi-walled nanotube.
In Example 2, the method of Example 1 optionally is performed such
that the act of extracting includes successively extracting lower
order nanotubes.
In Example 3, the method of one or any combination of Examples 1-2
optionally is performed such that the act of extracting includes
extracting a double-walled nanotube.
In Example 4, the method of one or any combination of Examples 1-3
optionally is performed such that the act of extracting includes
extracting a lower order nanotube with a different conductivity
property than the multi-walled carbon nanotube.
In Example 5, the method of one or any combination of Examples 1-4
optionally comprises supporting the at least one extracted lower
order nanotube by a substrate.
In Example 6, the method of one or any combination of Examples 1-5
optionally comprises applying pressure to the elongated side of the
multi-walled carbon nanotube to rupture the side of the
multi-walled nanotube before performing the extracting.
In Example 7, the method of one or any combination of Examples 1-6
optionally comprises: coupling a probe to the elongated side of the
multi-walled carbon nanotube; using the probe, moving the
multi-walled carbon nanotube in a direction perpendicular to a
longitudinal direction of the multi-walled carbon nanotube;
breaking an outer portion of the multi-walled carbon nanotube,
using the probe, thereby exposing at least one lower order carbon
nanotube; and extracting at least one lower order carbon nanotube
through a first break in the outer portion of the multi-walled
carbon nanotube.
In Example 8, the method of one or any combination of Examples 1-7
optionally comprises breaking an outer portion of at least one
lower order carbon nanotube, thereby exposing at least one further
lower order carbon nanotube.
In Example 9, the method of one or any combination of Examples 1-8
optionally comprises forming the multi-walled carbon nanotube in a
direction that is substantially parallel to a gaseous flow
direction.
In Example 10, the method of one or any combination of Examples 1-9
optionally comprises forming the multi-walled carbon nanotube with
a length limited by at least one of: a dimension of a surface, a
dimension of a substrate, a dimension of a heated zone, or a flow
characteristic.
In Example 11, the method of one or any combination of Examples
1-10 optionally comprises forming a nanotube catalyst, comprising:
forming a catalytic precursor including ferric chloride;
calcinating the catalytic precursor; and forming iron particles
with a size and density determined by a molar concentration of the
ferric chloride.
In Example 12, the method of one or any combination of Examples
1-11 optionally comprises patterning the catalytic precursor.
In Example 13, the method of one or any combination of Examples
1-12 optionally comprises patterning the catalytic precursor,
wherein the act of patterning comprises at least one of drop
drying, stamping, or photolithography.
In Example 14, the method of one or any combination of Examples
1-13 optionally comprises forming the multi-walled nanotube, which
comprises: forming a catalyst on a surface in a chamber; providing
a first gaseous flow in a first region of the chamber; and
restricting the first gaseous flow in a second region of the
chamber adjoining the surface to produce a second gaseous flow in
the second region, the second gaseous flow being less turbulent
than the first gaseous flow.
In Example 15, the method of one or any combination of Examples
1-14 optionally comprises forming a zero flow boundary region
between the first and second regions.
In Example 16, the method of one or any combination of Examples
1-15 optionally comprises restricting a gaseous flow, wherein the
restricting comprises generating a laminar flow by adjusting a
first chamber dimension relative to a second chamber dimension.
In Example 17, the method of one or any combination of Examples
1-16 optionally comprises restricting a gaseous flow, wherein the
restricting comprises generating a laminar flow by placing a tube
in the chamber to create the second region within the tube such
that the second gaseous flow is within the tube and is less
turbulent than the first gaseous flow in the chamber and outside
the tube.
Example 18 describes a carbon nanostructure manufacturing
apparatus. In this example, the apparatus comprises a heating
element; a first chamber region, coupled to the heating element,
the first chamber region providing a first gaseous flow; and a
second chamber region, located within the first chamber region, the
second chamber region restricting the first gaseous flow to provide
in the second chamber region a second gaseous flow that is less
turbulent than the first gaseous flow, the second chamber region
configured for housing a substrate for forming a carbon
nanotube.
In Example 19, the apparatus of Example 18 is optionally configured
such that the second chamber region is dimensioned and shaped to
provide a second gaseous flow having a Reynolds number of less than
2000 and the first chamber region is dimensioned and configured to
provide a first gaseous flow having a Reynolds number that exceeds
2000.
In Example 20, the apparatus of one or any combination of Examples
18-19 optionally is configured such that the first and second
chamber regions define respective first and second longitudinal
central axes.
In Example 21, the apparatus of Example 20 optionally is configured
such that the first and second longitudinal central axes are
substantially offset from each other.
In Example 22, the apparatus of Example 20 optionally is configured
such that the first and second longitudinal central axes are
substantially coincident with each other.
In Example 23, the apparatus of one or any combination of Examples
18-22 optionally comprises a first cylinder defining the first
chamber region and a second cylinder defining the second chamber
region.
Example 24 describes an apparatus comprising: M telescopingly
coupled carbon nanotubes, each of the M nanotubes having an
associated electronic band gap energy E.sub.Mi; and N telescopingly
coupled nanotubes, each of the N nanotubes having an associated
electronic band gap energy E.sub.N, wherein at least one of the M
nanotubes is coupled to at least one of the N nanotubes.
In Example 25, the apparatus of Example 24 is configured such that
the at least one of the M nanotubes that is coupled to the at least
one of the N nanotube have substantially equal E.sub.M and
E.sub.N.
In Example 26, the apparatus of one or any combination of Examples
24-25 is optionally configured such that at least one of the M
nanotubes that is coupled to the at least one of the N nanotube
have substantially unequal E.sub.M and E.sub.N.
In Example 27, the apparatus of one or any combination of Examples
24-26 optionally comprises P telescopingly coupled carbon
nanotubes, each of the P nanotubes having an associated electronic
band gap energy E.sub.P, wherein at least one of the P nanotubes is
coupled to at least one of the M nanotubes or to at least one of
the N nanotubes.
In Example 28, the apparatus of Example 27 is optionally configured
such that E.sub.P for the at least one P nanotube coupled to the at
least one of the M nanotubes or the at least one of the N nanotubes
substantially unequal to at least one of E.sub.M or E.sub.N.
In Example 29, the apparatus of Example 27 is optionally configured
such that E.sub.P for the at least one P nanotube coupled to the at
least one of the M nanotubes or the at least one of the N nanotubes
is substantially equal to at least one of E.sub.M or E.sub.N.
Example 30 describes an apparatus comprising: a mechanical
oscillator, comprising a plurality of telescopingly coupled carbon
nanotubes; and wherein the plurality of telescopingly coupled
carbon nanotubes are configured to provide coupled mechanical
oscillations as a function of respective diameters of the
nanotubes.
In Example 31, the apparatus of Example 30 is optionally configured
such that the plurality of telescopingly coupled carbon nanotubes
are configured in a necklace-like structure.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings, which are not necessarily drawn to scale, illustrate
generally, by way of example, but not by way of limitation, various
embodiments discussed in the present document.
FIG. 1 illustrates an example of a growth apparatus.
FIG. 2 illustrates an example of a method.
FIG. 3. illustrates an example of a method.
FIGS. 4A-4D illustrate examples of nanotubes.
FIG. 5 illustrates an example of a nanotube.
FIG. 6 illustrates an example of a method of extracting
nanotubes.
FIG. 7 is a cross-sectional view that illustrates an example of a
nanotube.
FIG. 8 is a side view illustrating an example of a nanotube.
FIG. 9 is a cross-sectional view illustrating an example of a
nanotube.
FIGS. 10A-B illustrate an example of a multi-walled carbon
nanotube.
FIG. 11 is a surface view illustrating an example of an
interconnected structure.
DETAILED DESCRIPTION
Multi-walled carbon nanotubes (MWNTs) can be used to form many new
electronic, optical, or mechanical devices. A MWNT provides an
elongated tubular structure that extends between first and second
ends, and that carries at least one other nanotube, which can be
referred to as a lower order nanotube or shell. A MWNT can carry a
single-walled carbon nanotube (SWNT), which does not carry another
nanotube within, or a MWNT can carry a lower order MWNT, which does
carry another nanotube within. In certain examples, MWNTs can be
formed that carry up to twenty concentric shells. The ends of the
MWNTs are closed, as are the ends of the successively carried lower
order inner shells. An inner shell can be extracted from its MWNT
outer shell in a telescope-like manner.
In an example, a lower order inner shell is extracted from its
outer shell by burning off an end cap of the outer shell with an
electrode, then spot welding a mechanical probe to the end of the
exposed inner shell, and then pulling on the mechanical probe to
extract the inner shell. Removal of the end cap by this process is
typically performed under vacuum in a transmission electron
microscope (TEM) with the MWNT attached to fixture at one end. The
process may not be practical for several reasons. First, the
extracted shell, including any of its concentric inner nanotubes,
is not free-standing, but rather is supported at one end by the
fixture and at the other end by the mechanical probe. Second, the
next inner shell cannot be extracted without burning off the end
cap of the extracted shell--but that end cap has been welded to the
probe. If the probe is removed (to enable the end cap to be
removed) the unsupported extracted nanotube can collapse or retract
into its outer shell under Van der Waals force. Therefore, this
process does not provide a practical method for successively
extracting inner shell nanotubes from a carrier outer shell
nanotube.
Growth of long MWNTs can be challenging. Chemical vapor deposition
(CVD) can typically produce a MWNT with a length that is on the
order of 50 microns or less. In such an example, a fully extracted
20-shell MWNT would have an end-to-end length that is less than 1
cm. This is four times less that a typical maximum length obtained
for a SWNT. If a particular diameter nanotube is desired to be
extracted from a MWNT, it is limited to the length of the outermost
shell of the MWNT. While longer SWNTs can be grown, a single, fixed
diameter shell does provide the design flexibility or structural
characteristics of MWNTs. For example, inner shells of the MWNT
have a hierarchical mechanical structure and a hierarchical
electronic band gap structure that can be exploited. Moreover due
to its concentric nature and the multiplicity of inner shells, a
MWNT can be mechanically stronger than a SWNT. The additional
strength of the MWNT can be used in a material to make it
stronger.
Discrete devices can be fashioned from MWNTs, but often with
limited lengths. One fabrication method involves burning away an
outer shell and sequentially working inward in a selected region by
a current-induced electrical breakdown mechanism. Electrodes can be
placed on the surface of the outermost shell. A current is passed
between the electrodes. At a high enough current, defects form
along the outmost shell. This increases the shell's electrical
resistance, which, in combination with the current, causes it to
get very hot. In ambient air, the outermost shell oxidizes and
eventually vaporizes. A third electrode can be placed in contact
with an outermost shell, such as between the two current
electrodes. A bias voltage can be applied to the third electrode,
such as to induce carrier depletion, thereby inhibiting current
flow between the first and second electrodes and protecting the
selected region of the shell in which the current is inhibited.
Such a shell-by-shell process is time consuming, and therefore, is
not readily scalable. For MWNTs of limited length, device
manufacture may be impractical. MWNT length limitations, therefore,
can inhibit developing new device structures and materials. Thus,
the present inventor has recognized that there is a need for long
MWNTs and for improved processing technologies.
The MWNTs described herein can include one or more nanotubes with
semiconducting properties or one or more nanotubes with metallic
properties. Such nanotubes can also be doped, such as to adjust
electrical properties or to form a specific device structure.
Electrical conduction between concentrically adjoining nanotubes
can be low enough to inhibit the flow of electrical charge between
them. Therefore, as described in further detail below, complex
electrical interconnection, devices, or circuits can be formed from
MWNTs.
FIG. 1 illustrates an example of a growth apparatus. In this
example, a reactor 100 includes an outer chamber 102 and an inner
chamber 104. The inner chamber 104 is shorter than the outer
chamber 102. A substrate 106 is placed inside the outer chamber
102, such as within the inner chamber 104. A heat source 110 is
coupled to the reactor 100, such as to provide heat to the
substrate 106. The heat source 110 can be coupled to a current,
voltage, or radio frequency (RF) source such as a microwave
generator. The substrate 106 can be supported by a susceptor 108,
which may be a source of heat. The susceptor 108 can include a
resistive heating element. In certain examples, the susceptor 108
can be made of alumina or silicon carbide coated with a metal
catalysts, such as iron and cobalt.
An average boundary layer thickness of a gaseous stream flowing
over a flat surface can be represented by the approximation
.DELTA..times..intg..times..delta..function..times..times.d.times.
##EQU00001## where L is the length of the flat surface, .delta.(x)
is the boundary layer thickness, and Re.sub.L is the Reynolds
number. A Reynolds number can help characterize flow by providing a
measure of a ratio of the inertial forces to the viscous forces. A
small Reynolds number indicates that viscous forces predominate. A
large Reynolds number indicates that inertial forces predominate.
For a reactor 100 with a tubular geometry, the Reynolds number can
be expressed by .rho.vd/.gamma., where .rho. is the density of the
gasses, v is the velocity of gas steam, d is the tube diameter, and
.gamma. is the kinematic coefficient of viscosity. In general,
laminar flow exists in a region if the associated Reynolds number
for the region is less than about 2000. Thus, the Reynolds number
can be used to distinguish laminar flow from turbulent flow, such
as where a reactor region providing laminar flow is desired. In
particular, for growing long carbon nanotubes, it can be desirable
to provide laminar flow in the region adjacent to the surface of
the substrate.
The outer chamber 102 and an inner chamber 104 can cooperate in
generating a laminar flow in the inner chamber, even when there
exists more turbulent flow in the outer chamber. Each chamber can
be sized and positioned relative to the other so as to create and
maintain laminar flow in the inner chamber 104 during growth of
carbon nanotubes. In an example, the outer chamber 102 and the
inner chamber 104 are non-concentric, horizontally aligned tubes,
such as shown in FIG. 1. In the example of FIG. 1, a longitudinal
center axis of the tubular outer chamber 102 is offset from a
longitudinal center axis of the tubular inner chamber 104. In other
examples, the inner chamber 104 and the outer chamber 102 are in
concentric alignment. The outer chamber 102 and the inner chamber
104 can have different shape cross-sections, but the inner chamber
104 will restrictively guide the first gaseous flow in the outer
chamber 102 to produce a less turbulent and preferably laminar
second gaseous flow within the inner chamber 104. This technique
can provide a stable gaseous flow pattern at a leading edge of a
growing nanotube at the substrate 106. Some examples of such
tubular cross-sections include a square, a rectangle, a polygon, a
circle, or an ellipse. Although the reactor 100 is shown as a
horizontal arrangement of chambers, a vertical arrangement can also
be used, such as to provide laminar flow in the boundary layer
adjoining the surface of the substrate 106 during carbon nanotube
growth.
Since the Reynolds number of a gaseous flow is a function of gas
viscosity and gas density, the geometry of the inner chamber 104
can be adjusted to accommodate various flows of various reaction
gasses or concentrations. Chamber pressures in the outer chamber
102 or the inner chamber 104 can likewise be adjusted, such as to
obtain laminar flow adjacent to the substrate 106. The ability to
adjust chamber pressure, inner chamber 104 geometry, or outer
chamber 102 geometry, can advantageously provide a degree of
latitude in the chemical composition or dilution of the reaction
gases that can be used.
FIG. 2 illustrates an example of a method 200. At 202, a catalytic
precursor is formed. The catalytic precursor can be used for
generating a carbon nanotube growth catalyst. In an example, the
catalytic precursor comprises a solution of FeCl.sub.3 having a
molar concentration ranging from of 0.001 to 0.1 in a mixture of
water and ethanol. At 204, the catalytic precursor can be patterned
at desired locations near a substrate edge or anywhere else on a
substrate 106, such as by drop drying or stamping. The precursor
can also be patterned by spin drying or by photolithographic
processes, such as using a photoresist or a polyimide. The
substrate 106 can be any suitable material resistant to deformation
at the high temperatures used for carbon nanotube growth. Some
examples of substrates include silicon, silicon carbide, gallium
nitride, or oxides or nitrides of silicon, aluminum, tantalum,
titanium, tungsten, or the like. The substrate 106 can have a flat
surface to receive the catalytic precursor for carbon nanotube
growth.
At 206, the patterned catalytic precursor is calcinated. In an
example, the patterned catalytic precursor is calcinated at a
temperature of about 950.degree. C. for 30 minutes in mixture of
hydrogen flowing at 60 sccm and argon flowing at 200 sccm. Other
inert gases can be substituted for the argon. In this example of
the process, this results in formation of iron particles on a
surface of the substrate 106. The relationship between the
catalytic precursor and the resulting iron catalyst can be
described by the balancing equation
.times..times..times..times..times..times..function..times..fwdarw..DELTA-
..times..degree..times..times..times..times..times..times..function..times-
..times..times..function. ##EQU00002## where n is an integer value
greater than or equal to 1. The resultant iron particles can serve
as a catalyst for initiating growth of carbon-based nanotubes, such
a SWNTs and MWNTS, or other structures.
After the desired pattern or arrangement of iron particles is
formed, carbon nanotubes can be grown from such locations of the
iron particles. The size and density of the iron particles can
depend upon the molar concentration of the FeCl.sub.3. The number
of MWNTs formed relative to the number of SWNTs can also depend on
the molar concentration of FeCl.sub.3, as illustrated in Table I.
In general, if the preference is toward an increasing number of
SWNTs, the molar concentration of FeCl.sub.3 can be decreased. The
average diameter of the nanotube also decreases with a deceasing
molar concentration of FeCl.sub.3 in the precursor solution.
TABLE-US-00001 TABLE I Precursor Concentration (in water &
ethanol) FeCl.sub.3 0.1M FeCl.sub.3 0.01M FeCl.sub.3 0.001M
Dominant Shell Type MWNT MWNT + SWNT SWNT Average Diameters 3.3 nm
2.4 nm 1.8 nm Standard Deviation 1.0 nm 0.7 nm 0.4 nm
FIG. 3. illustrates an example of a method 300. At 302, iron
particles are formed on a surface of a substrate 106. The iron
particles can be formed using method 200, as described above. In
certain examples, catalytic precursors with molar concentrations
ranging from 0.001 to about 0.1 FeCl.sub.3 are patterned on an
SiO.sub.2 surface of a silicon wafer substrate 106. Each iron
particle can serve as a catalyst for a nanotube growth. Therefore,
in certain examples, a linear arrangement of multiple iron
particles can be positioned to receive a perpendicular gas flow so
as to serve as catalysts for forming an array of nanotubes
extending along the surface of the substrate in a direction that is
perpendicular to the linear arrangement of the multiple iron
particles.
The iron particles can be formed on a surface of the substrate 106
in the same reactor 100 used to grow the nanotube structures
described herein. Iron particles can also be formed on a substrate
106 in a first reactor, and then the substrate 106 can be
transferred to second reactor 100 that is configured for growing
carbon nanotubes. If so, the outer surfaces of the iron can be
protected from oxidation or the accumulation of carbon-containing
compounds. For example, a volatile material that does not react
with iron can be formed over the iron particles, or the iron
particles can be enclosed in inert atmosphere or vacuum environment
before and during the transfer. For example, a vacuum environment
can be provided with a load-locked chamber coupling the reactor
used for generating the iron catalyst with the reactor used for
nanotube growth. Similarly, a vacuum "briefcase" can also be used
during transfer of the substrate 106 between reactors.
At 304, laminar gaseous flow conditions are created across the
surface of the substrate 106 carrying the iron particles that are
used as catalysts for carbon nanotube growth. Laminar flow
conditions near the surface of the substrate 106 can be promoted by
suitably adjusting the Reynolds number for the flow, such as by
selecting one or more growth or apparatus parameters. For example,
laminar flow conditions can be promoted by adjusting at least one
of a reactor geometry, a gas flow rate, a gas composition, a gas
viscosity, a gas density, or a chamber pressure. In certain
examples, laminar flow is promoted at a boundary region adjoining
the surface of the substrate 106. Advantageously, such laminar flow
can be promoted by using the inner chamber 104 and outer chamber
102 as described with respect to FIG. 1. In certain examples,
laminar flow is promoted in a reactor region including a boundary
region adjoining the surface of the substrate. Once laminar flow is
obtained, the conditions responsible for laminar flow can be varied
in a manner that helps maintain the laminar flow in the boundary
region adjoining the substrate 106.
At 306, nanotube structures are formed extending longitudinally
away from the iron particles. During formation, the resulting
nanotube structures can extend above and along a top surface of the
substrate 106; when the gaseous flow ceases, the resulting nanotube
structures will typically fall back to rest upon the top surface of
the substrate 106. Elongated MWNTs longer than 10 cm can be grown a
temperature of about 950.degree. C. in a 30 cm long reactor 100.
Carbon nanotube growth temperatures ranging between about
920.degree. C. and about 970.degree. C. can be used. Methane
flowing at a rate of 100 sccm and hydrogen at a rate of 60 sccm can
be concurrently introduced into reactor 100 and passed over a top
surface of the substrate for 3 hours. A Reynolds number of 50 near
the top surface of the substrate 106 in the reactor 100 is
estimated for the above parameters. An increasing Reynolds number
generally yields a decreasing nanotube length.
FIGS. 4A-4D illustrate certain examples of resulting nanotubes,
such as can be obtained using the processes and apparatuses
described herein. FIG. 4A is a surface view of carbon nanotubes
grown under turbulent flow conditions in the boundary region
adjoining a SiO.sub.2 surface of a silicon substrate 404A. The
corresponding catalytic precursor concentration was 0.1 M
FeCl.sub.3. In the example of FIG. 4A, the resulting nanotube
structures 402A are irregularly shaped and are predominately
SWNTs.
FIGS. 4B-C illustrate examples of surface views of carbon nanotubes
grown with laminar flow in the boundary region adjoining an
SiO.sub.2 surface of silicon substrates 404B-C. In these examples,
the Reynolds number is estimated at about 50. The catalytic
precursor concentrations used in this example for the nanotube
growth are 0.01 M FeCl.sub.3 for FIG. 4B and 0.1 M FeCl.sub.3, for
FIG. 4C, respectively. Nanotube structures 402B and 402C are
regularly shaped and predominately MWNTs. The growth direction of
the elongated nanotube structures is substantially parallel to the
direction of laminar gas flow. In contrast, FIG. 4D illustrates an
example in which, for a Reynolds number of 50 and a concentrations
0.001 M FeCl.sub.3, the resulting nanotube structures 402D are
predominantly SWNTs. However, under laminar flow obtainable using
the apparatus of FIG. 1 and these conditions, the resulting SWNTs
are more regularly shaped than those grown with a less laminar and
more turbulent flow.
The growth apparatus and processes described herein permit
formation of MWNTs and SWNTs of lengths that need not be
structurally limited by end cap formation or growth dynamics. The
MWNT and SWNT structures can be grown as long as the configuration
of the reactor 100 and the substrate 106 permits. In the
above-described examples, a silicon substrate 106 was selected
merely because it is readily available at a low cost; it can easily
provide a reusable, ultra-flat surface with lengths of up to 300
mm. Therefore, using such a substrate 106, up to 30 cm long MWNTs
can be formed--which, when inner shells are successively extracted,
can yield total lengths of up to 6 meters for a fully extracted
MWNTs with 20 shells. Other substrates can also be used, such as
sapphire or silicon carbide, for example. By increasing the length
of the heated zone and by use of longer substrates, MWNTs with even
greater lengths may be grown.
FIG. 5 schematically represents an example of a nanotube that can
be formed such as described herein. In the example of FIG. 5,
trenches 506 or even via through holes can be formed in a substrate
502. In an example, the trenches 506 can have widths ranging from
100-500 microns and depths of 0.5 mm. The reactor geometry and
growth processes described in FIGS. 1-3 can be used to generate
laminar gas flow across the surface of the substrate 502, such as
in a direction that is substantially perpendicular to the trenches
506. In this example, a nanotube 504 structure can be grown across
such trenches 506 as a single, continuous SWNT or MWNT. Therefore,
under such conditions, the trenches 506 apparently do not
substantially disrupt the laminar flow obtained in the boundary
layer adjoining the surface using the processes and apparatuses
described above.
Thus, the substrate 106 need not be unitary. Instead, planar
substrates can be sawn perpendicular to a surface, polished along
the sawn edge and butted against one another to form a continuous
substrate that provides an arbitrary length platform for nanotube
growth. As made clear by FIG. 5, a separation between adjoining
substrates can be at least 500 microns. Laminar flow can be
maintained in the surface boundary regions of the adjoining
substrates to form elongated SWNTs and MWNTs across the boundary
regions as continuous structures. Production extremely long SWNTs
and MWNTs is therefore possible. The reactor can be lengthened
while maintaining laminar flow conditions by distributing or
otherwise employing one or more vacuum pumps to increase the mean
free path of the gas, and to adjust the thickness of the boundary
layer adjoining the growth surfaces. A moving growth platform
arrangement can also be used with a sequentially differentially
pumped chamber, such as to permit removal of arrays of SWNTs and
MWNTs without introducing contamination or having to stop the
growth process.
Before nanotube growth, the trenches 506 can be filled with a
metal, such as a refractory metal, or a conductive metal alloy
having a high melting point. A chemical mechanical planarization
(CMP) process can by used to planarize trenches 506 so that
nanotube 504 forms and electrically contacts the metal. Such
cross-connects can be used, for example, to form interconnections
such as substrate wordlines or bitlines, particularly where the
nanotube 504 exhibits a conductive property. This technique can
also be used to form gated transistors or logic circuits, such as
when the nanotube 504 exhibits a semiconducting property, such as
described below.
FIG. 6 illustrates an example of a method 600 of extracting one or
more lower order inner nanotube shells from a carrying outer shell.
At 602, a probe is coupled to an elongated sidewall portion between
the ends of an outer shell of a MWNT structure. The force coupling
the probe to the outer shell can be a cohesive mechanical contact
force or an electrostatic force sufficient to apply pressure. In an
example, an atomic force microscope (AFM) tip is coupled to an
outer shell of a MWNT supported by a substrate, such as in a
direction substantially parallel to its growth direction.
At 604, the probe is moved a direction that is substantially
perpendicular to the elongated growth direction of the MWNT. In
certain examples, an AFM tip is moved at a rate of between 0.5-0.8
cm/s in a direction substantially perpendicular to the elongated
growth direction. The MWNT may be laterally pushed or pulled by the
probe. Such movement in effect, drags the MWNT across the surface
of the substrate in a general direction that is perpendicular to
the nanotube growth direction.
At 606, the lateral probe movement and continues until a tensile
strength (e.g., between 10 GPa and 100 GPa, due to friction between
the MWNT and the substrate's surface) is exceeded. When this
occurs, the outer shell of the MWNT circumferentially ruptures,
thereby exposing the next inner shell. This exposed next inner
shell can carry other nanotubes, or it can be the inner-most
nanotube, which does not carry any other nanotubes. If desired, the
probe can then be used to couple to the exposed next inner shell,
such as by cohesive mechanical contact or electrostatic force, such
as to apply pressure to such next inner shell to either
telescopingly extract or rupture the next inner shell, as
desired.
At 608, the probe is moved in a direction other than in the
elongated growth direction. Adjacent concentric nanotubes are
coupled together by Van der Waals forces. This Van der Waals force
between adjacent concentric nanotubes can be overcome by applying
pressure with the mechanical probe, such that the next inner shell
can be telescopingly extracted, along with any further nanotube
shells contained therein. This process of successively extracting
the next inner shell can continue until the critical tensile
strength is again reached for the next inner shell. This ruptures
the next inner shell, thereby exposing any further inner shell(s)
carried therewithin. The extraction process can be repeated until
there are no further inner shells remaining to extract. The
extraction process can be used to completely extract an inner shell
from its carrier outer shell, or an overlapping region can be
retained, such that the combination of adjacent shells together
form a longer cohesive structure, in a manner similar to a
retractable and extendable telescope.
The length of a shell that can be extracted before
circumferentially breaking is influenced by friction between the
substrate and shell undergoing extraction. The extraction length
can be increased if probe is used to guide the shell being
extracted above the surface of the substrate to reduce such
friction. Surface friction can also be reduced by use of a suitable
surface lubricant or by using a surface with low friction
coefficient. The shells need not be extracted on the growth
surface; for example, a MWNT can be moved to another surface before
extracting inner shells from a MWNT.
FIG. 7 illustrates an example of a cross-sectional view of a MWNT
undergoing successive shell extraction such a described above with
respect to the method 600. For illustrative clarity, this example
only shows three shells, however, a different number of shells can
be used. Before extraction, the MWNT 700A includes outermost shell
702A and successive concentric inner shells 704A and 706A of
approximately equal length.
MWNT 700B illustrates subsequent partial extraction of shells 704B
and 706B through a circumferential break 710B in the elongated side
portion between the ends of nanotube 702B. In this illustrative
example, the lengths of shells 704B and 706B remaining within the
shell 702B are approximately equal. The arrow R represents the
general direction of probe movement.
MWNT 700C illustrates subsequent partial extraction of shell 706C
through a circumferential break 712C in the elongated side portion
between the ends of nanotube 704C. If shell 706C carried one or
more other shells, further extraction can similarly be performed.
The arrow S represents the general direction of probe movement.
Friction between shell 704C and the substrate surface can be used
to inhibit nanotube 704C from being drawn through break 710B back
into nanotube 702C by Van der Waal forces.
FIG. 8 is a side view illustrating an example of a nanotube
structure. In this example, double-walled nanotubes (DWNTs) are
successively extracted from a MWNT. A DWNT comprises a pair of
SWNTs coupled together by an additional deforming force. The arrows
indicate the direction of probe movement. The corresponding height
profile is also shown in FIG. 8. FIG. 8 shows that there is a step
change in the diameter of the MWNT 802 of about 1.4 nm in the
vicinity where DWNTs 804 and 806 are extracted through breaks 808
and 810, respectively. The successive change in diameter is about
four times the intershell spacing of 0.35 nm. The plateau lengths
for DWNTs 804 and 806 are up to 500 .mu.m. SWNTs extracted under
similar conditions provide plateau lengths of about 100 .mu.m. The
greater lengths of the extracted DWNTs may be due to increased
friction between DWNT shells arising from surface induced
deformation of the outer shell of the pair. Therefore, the DWNT may
be particularly useful for providing strength in materials, such as
in strengthening fabrics and building materials.
FIG. 9 is a cross-sectional view of an example of a nanotube, such
as can be formed using the method 600 described above. For
illustrative clarity, only two shells are shown here, however, a
different number of shells could be used. In this example, the MWNT
900 includes an outer shell 902 carrying a concentric inner shell
904, which, in turn, can carry one or more other shells. In this
example, the shell 902 is broken circumferentially at locations 906
and 908 on the elongated side between the ends of the MWNT 900. In
this example, the shell 904 can be partially extracted in opposite
directions. This illustrates the mechanical flexibility of the
structure. The shell 902 can be further broken at a third or more
different locations as desired. Although FIG. 9 illustrates MWNT
900 with nanotubes being extracted in opposing directions, shell
904, and any shells carried therein, can be extracted at any
desired angle. This includes extraction perpendicular to the plane
of the substrate surface supporting the MWNT 900. This added degree
of dimensional freedom permits forming complex patterns of
nanotubes using the MWNTs and methods described. For example,
flexible interleaved structures can be formed of SWNTs, DWNTs, or
MWNTs to strengthen materials such as glues, adhesives, concrete
mixtures, metals, metal alloys, and articles of clothing. The
SWNTs, DWNTs, or MWNTs can be separated from a substrate's surface
and randomized to form a wool-like pattern. Carbon nanotube
structures can be woven or twisted together forming a cable-like
structure to further increase strength. Thread, cable and mesh
arrangements may also be incorporated in other materials to
increase overall strength, for example, in materials used for
airframes, automobile bodies, automobile body parts, wallboard,
flexible armor, bulletproof vests, transport containers, and the
like. Since stable and flexible SWNTs, DWNT, or MWNTs are formed at
high temperatures, they may be usable in forming light-weight fire
retardant fabrics. Such fabrics include children pajamas,
firefighting equipment, fire shelters, furnace insulation, or the
like.
FIG. 10A illustrates an example of a MWNT arrangement. For
illustrative clarity, this example shows only three shells,
however, a different number of shells could be used. In the example
of FIG. 10A, a fast extraction (e.g., a shell extraction velocity
of greater than about 0.1 min/sec) is used to draw a plurality of
inner nanotube shells from within the outer tube of the MWNT 1000A.
In this example, the MWNT 1000A includes an outer shell 1002A and
the successive next two inner shells, 1004A and 1006A,
respectively. During extraction, the outer shell 1002A can be
circumferentially broken at 1008A. This can be accomplished by
moving a probe 1010A, while it is coupled at a location along the
elongated tubular sidewall extending between the ends of MWNT
1000A. The probe can be moved in a direction (indicated by arrow Q)
that is approximately perpendicular to the elongated growth
direction (indicated by arrow T). By continuing to move probe 1001
in this direction, the next inner shells 1004A and 1006A can be
extracted. In this example, the shell 1004A undergoes repeated
breaking along its circumference, thereby exposing shell 1006A and
forming portions 1014A in a region that is not coupled to the
probe. The shell 1006A can include one shell, or it can carry
additional shells. This extraction process can be used to form of a
quasi-periodic structure. The probe velocity or the friction forces
between the shells being extracted and a supporting substrate
surface may be adjusted, such as to vary a length of portions
1014A.
FIG. 10B illustrates an example of a useful resulting MWNT
structure. For illustrative clarity, this example shows only three
shells, however, a different number of shells could be used. In
this example, the MWNT 1000B includes concentric shells 1002B,
1004B, and 1006B. The shell 1006B can carry one or more additional
shells. The MWNT 1000B can be one of the portions 1014A described
above. A SWNT has a radial breathing mode that is approximately
inversely proportional to its diameter d.sub.n
.omega..sub.n.alpha.1/d.sub.n where .omega..sub.n is its mechanical
frequency of oscillation. Therefore, a MWNT with n shells can have
at least n localized oscillation frequencies. These oscillations
can occur with frequencies in the GHz range. For example, if MWNT
1000B is one of the portions 1014A, each such portion can have
substantially the same mechanical oscillation frequencies. In
certain examples, the oscillation can be coupled to increase an
oscillation magnitude at a specified frequency. The oscillation can
also be coupled, in certain examples, to generate frequencies
having in-phase and out-of-phase locked modes. The mechanical
oscillation can also be coupled in such a way as to generate one or
more beat frequencies. Such characteristics can be used to make
devices such as mechanical resonators, switches, or transducers
operating in the GHz range.
The MWNT structures disclosed herein can include nanotubes having
semiconducting properties or metallic/conducting properties. Each
inner shell carried within a MWNT has an associated band gap
energy. The band gap energies are generally inversely proportional
to the shell diameter. Extracted nanotube shells can also include
portions having both semiconducting and metallic properties. The
length of a nanotube shell, its diameter, and conductivity type can
be selected to provide a specified conduction characteristic. The
nanotubes may be doped to further modify the electrical
characteristics. Because inter-shell conduction can be low enough
to inhibit charge transfer between concentrically adjoining
nanotubes, the electrical properties of a nanotube can be exploited
to form various band gap engineered interconnected structures.
FIG. 11 is a surface view illustrating an example of an
interconnect structure. In this example, only four MWNTs are shown
for illustrative clarity, however, a different number of MWNTs or
shells could be used. MWNT 1110, 1120, 1130 and 1140 can include a
different numbers of inner shells. One or more of MWNT 1110, 1120,
1130 and 1140 be can be extracted from a same or a different base
MWNT (not shown). MWNT 1110, 1120, 1130 and 1140 can have metallic
properties, or same or different semiconducting properties. The
lower order inner shells can be extracted to a desired length.
In this example, the shells 1114 and 1144 are in contact, the
shells 1128 and 1148 are in contact, and the shells 1136 and 1146
are in contact. Each of these shells can be in further contact with
one or more other structures or devices. Each shell can also form a
portion of an electronic device, such as a transistor. For example,
if the shell 1146 has metallic properties and the shell 1136 has
semiconducting properties, a Schottky contact can be formed and the
two shells form a Schottky diode. If the shell 1128 and the shell
1148 each have semiconducting properties, then a semiconductor
junction can be formed with a band gap energy discontinuity, if
desired. If the shells 1128 and 1148 are coupled to a bias
potential, the region providing the band gap energy discontinuity
can be used to block carrier flow or to enhance carrier injection.
If the shells 1128 and 1148 have opposite conductivity types, then
a p-n junction can be formed. If the shells 1114 and 1144 each have
metallic properties, then metal-like interconnection can be formed.
Therefore, by the appropriate connection of the shells, p-n
junction diodes, Schottky diodes, field effect transistors (FETs),
and bipolar junction transistors (BJTs) can be formed from the
shells of MWNTs 1110, 112, 1130, and 1140. Since the extraction of
the inner shells yields different electrical properties than the
outer shell, the extraction can play an important role in tailoring
the electrical characteristics to obtain the desired device. Such
devices can provide building-blocks that can be integrated at the
nanoscale level, such as by interconnection using shells having
metallic properties. This further permits more complex electrical
and electromechanical structures such as photodetectors, memory
cells, voltage controlled oscillators, heterodyne circuit and the
like to be fabricated from the ultralong MWNTs disclosed herein,
and the shells that can be extracted therefrom.
Closing Notes
The above Detailed Description includes references to the
accompanying drawings, which form a part of the Detailed
Description. The drawings show, by way of illustration, specific
embodiments in which the invention can be practiced. These
embodiments are also referred to herein as "examples." All
publications, patents, and patent documents referred to in this
document are incorporated by reference herein in their entirety, as
though individually incorporated by reference. In the event of
inconsistent usages between this document and those documents so
incorporated by reference, the usage in the incorporated
reference(s) should be considered supplementary to that of this
document; for irreconcilable inconsistencies, the usage in this
document controls.
In this document, the terms "a" or "an" are used, as is common in
patent documents, to include one or more than one, independent of
any other instances or usages of "at least one" or "one or more."
In this document, the term "or" is used to refer to a nonexclusive
or, such that "A or B" includes "A but not B," "B but not A," and
"A and B," unless otherwise indicated. In this document, the term
"subject" is used to include the term "patient." In the appended
claims, the terms "including" and "in which" are used as the
plain-English equivalents of the respective terms "comprising" and
"wherein." Also, in the following claims, the terms "including" and
"comprising" are open-ended, that is, a system, device, article, or
process that includes elements in addition to those listed after
such a term in a claim are still deemed to fall within the scope of
that claim. Moreover, in the following claims, the terms "first,"
"second," and "third," etc. are used merely as labels, and are not
intended to impose numerical requirements on their objects.
The above description is intended to be illustrative, and not
restrictive. For example, the above-described examples (or one or
more features thereof) may be used in combination with each other.
Other embodiments can be used, such as by one of ordinary skill in
the art upon reviewing the above description. Also, in the above
Detailed Description, various features may be grouped together to
streamline the disclosure. This should not be interpreted as
intending that an unclaimed disclosed feature is essential to any
claim. Rather, inventive subject matter may lie in less than all
features of a particular disclosed embodiment. Thus, the following
claims are hereby incorporated into the Detailed Description, with
each claim standing on its own as a separate embodiment. The scope
of the invention should be determined with reference to the
appended claims, along with the full scope of equivalents to which
such claims are entitled.
The Abstract is provided to comply with 37 C.F.R. .sctn.1.72(b), to
allow the reader to quickly ascertain the nature of the technical
disclosure. It is submitted with the understanding that it will not
be used to interpret or limit the scope or meaning of the
claims.
* * * * *